Evolium™ Base Station Subsystem (BSS) Description

© Alcatel University - 8AS 90200 1338 VT ZZA Ed01

Evolium Base Station Subsystem (BSS)

Description

© Alcatel University - 8AS 902001338 VT ZZA Ed01

Evolium BSS DescriptionCourse content

S1 : Evolium Base Station Subsystem introduction

S2 : Operation and Maintenance principles


Session 1

EvoliumTM Base Station System Introduction


S1 : Evolium BSS introductionObjective and program

Objective : To describe the Evolium BSS network

Program : Functions Architecture Telecom features Cell Types


Base Station Subsystem

The very first aim of a communication system is to transport user information (speech or data).

Network SubSystem

MobileStations

Public Land Mobile Network Public Switched Telephone Network or Packet Data Network

S1 : Evolium BSS introduction Functions

Mobile telecommunication overview


Evolium BSS Description Functions

The main role of the BSS is to provide and support both bi-directional signalling and traffic channels between Mobile Stations and the Network Switching System which is in charge to manage communications within the Public Land Mobile Network (PLMN) (Mobile to Mobile calls) and

- the Public Switched Telephone Network (Mobile /Fixed telephone calls in circuit switching mode)

- Packet Data Network in packet switching mode



BSS functions (1) : CALL SETUP The BSS provides radio coverage (signalling and traffic channels)

between Mobiles and the NSS.

MOBILITY MANAGEMENT Location updating

SUPPLEMENTARY SERVICE Short Message Service

USER TRAFFIC Speech Data



Call set up is required to establish communication between an MS and the NSS

Mobility Management : These calls, e.g. location update, are used by the system to gather MS information. The exchanges are protocol messages only; therefore, only a signaling channel is used.

Supplementary Service : These calls, e.g. SMS and SS calls, pass small amounts of information. Therefore, only a signaling channel is used.

User Traffic : These calls, e.g. speech or data calls to a correspondent, can pass large amounts of information. Therefore they require greater bandwidth than a signaling channel. These calls use traffic channels.

The channels used for calls are the SDCCH for signaling and the TCH for user traffic. An SDCCH is always assigned for call set up, even if a TCH is later required for the call.



BSS functions (2) : CALL HANDLING IN CALL MODIFICATION

Speech or data / Fax

HANDOVER Type : Inter cell external / Inter cell internal / Intra cell Cause : Better cell / Bad quality / Bad received level /

Interference / Mobile Velocity / Traffic / Congestion / Preferred band

CIPHERING no / A5-1 / A5-2

OVERLOAD CONTROL BSC / BTS



An obvious requirement for the effective management of calls in the BSS is to provide the following:

Maximum perceived signal quality with minimum perceived interference.

Call continuity regardless of changes in propagation conditions or change of location of the MS.

The supervision of calls in progress is provided by the Call Handling function.

Call Handling functions and features include: In-Call Modification Frequency Hopping Discontinuous Transmission Radio Power Control Handover (the objective is to reduce HO timing)



BSS Functions (3) : CALL RELEASE

CALL RELEASE in normal service Calls terminated by call management Calls terminated following a channel change

SPECIAL CASE Call release following a reset BSC, BTS or MS initiated release



The Call Release procedures ensure that resources allocated to a call are free for reuse when they are no longer required by the current call.

Call Release procedures are required when: A call is finished and either the called or calling party hang up A MS is turned off A call is handed over and the resources for the original call are

released There is operator intervention, such as a channel being blocked There is a failure There is a radio link failure

If a call is terminated normally, the Call Release procedures are triggered automatically. If the call is terminated abnormally, the system has to detect that the resources are no longer required and release them.


MSC


BSS Functions (4) : Operation and Maintenance

To ensure that the BSS functions correctly, O&M actions are implemented at all levels within the BSS. The O&M functions

in the BSS are grouped into three categories:

CONFIGURATION Management FAULT/ ALARM Management PERFORMANCE Management\


PacketPacketSwitchingSwitchingNetworkNetwork InternetInternet

Packet Data Network

data

BSS

PSTNPSTN

NSS

(E)GPRSMobile

Stations

PLMN

speech


Evolution to (E)GPRS



data transmission over the air interface is limited to 9.6 kbps, too slow for use of graphics-intensive services.

GPRS General Packet Radio Service (GPRS). GPRS : maximum rate is 170 Kbps.

EGPRS EGPRS (Enhanced GPRS) is based on TDMA and offers a

maximum theoretical speed of 384 kbps. EGPRS compatible MTs are required. The BSS remains the same,

except for new EGPRS/GSM compatible TRXs to be added to each cell where EGPRS has to be activated.


PacketPacketSwitchingSwitchingNetworkNetwork


Evolution to (E)GPRS

(Enhanced) General Packet Radio Service is the solution chosen by 3GPP to answer the demand for increased data transmission rates.

Two parallel systems in the PLMN: Circuit-switched transmission for speech Packet-switched transmission for data


PSTNPSTNBSC

MobileStations

TC

BTS

BTS

PLMN

BSSNSS

S1 : Evolium BSS introduction Architecture

BSS components in the PLMN (Circuit Switching) BTS: Base Transceiver Station (which provides the radio links

between the Mobile Stations and the BSC.) BSC: Base Station Controller (which controls several BTSs) TC: Transcoder (located between the BSC and the NSS)


PSTNPSTNBSC

MobileStations

TC

BTS

BTS

MSC

PLMN

BSSNSS

HLRVLRAuCEIR


NSS components in the PLMN (Circuit Switching) MSC: Mobile Switching Center

• HLR: Home Location Register• VLR: Visitor Location Register• AuC: Authentication Center• EIR: Equipment Identity Register


Evolium BSS DescriptionArchitecture

MSC: Mobile Switching Center It is a switching exchange whose main functions are:

Call Handling Specific GSM functions such as:

• Mobility Management: Communication with the Location Databases (VLR and HLR)• Handover execution when involved

Gateway Function for Terminating Call (TC)

HLR: Home Location Register It is a reference database where the following information are

stored: identities of the subscriber (international identity, directory number) subscribed services rough location of the Mobile Station (identification of the VLR where

the MS is now registered)


Evolium BSS DescriptionArchitecture

VLR: Visitor Location Register The VLR is associated with one or more MSC. It is a local

database with the following information: Copy of the HLR data for visiting subscribers More precise location of the Mobile Station (an area of the network

called “Location Area” which is a group of cells Call re-direction data

AuC: Authentication Center The AuC is the Security Database of GSM which generates the

parameters used during the Authentication and Ciphering procedures

EIR: Equipment Identity Register The EIR is a database where the identities of the Mobile

Equipment are stored and classified in black, grey and white list.


GGSNGGSNSGSNSGSNInternetInternet

IP GPRS IP GPRS BackboneBackbone

PSTNPSTNBSC

TC

BTS

BTS

MSC

(E)GPRSMobile

StationsHLR

speech

data


BSS components for (E)GPRS solution MFS: Multi-BSS Fast packet Server SGSN: Serving GPRS Support Node GGSN: Gateway GPRS Support Node

GSS: Gprs SubSystem

Alcatel 9135MFS


MSC

OMC-R

NMC

CBC

InternetInternetIP GPRS IP GPRS

BackboneBackbone

PSTNPSTNBSC

TC

BTS

BTS

MSC

HLR

GGSNGGSNSGSNSGSN

Alcatel 9135MFS


External components OMC-R: Operations & Maintenance Center - Radio NMC: Network Management Center CBC: Cell Broadcast center


MSC

OMC-R

CBC


BackboneBackbone

PSTNPSTNBSC

TC

BTS

BTS

MSC

HLR

GGSNGGSN

SGSNSGSN

Alcatel 9135MFS

A-bis A-ter mux

Gb

A


Interfaces in the BSS A-bis A-ter mux / A Gb

A-GPSserver

GMLC

NMC

Lh

Lg

GiSAGI Gn

GPS ReceiversReference network


S1 : Evolium BSS introduction Telecom features

Features defined in the GSM recommendations Cellular Environment : define different types of cell configurations to

meet the requirements of geography and the strategies of the Network Operator.

Frequency Hopping Radio Frequency hopping Base Band Frequency hopping

Radio Power Control uplink and downlink (BTS / MS) : uplink and downlink: ensure the dynamic balance between the quality of the radio link in both directions (i.e., uplink and downlink), against interference with other cells. It also contributes to power conservation.RPC is achieved through BTS Radio Power Control and MS Radio Power Control.

Enhance Full Rate (EFR) : allow the use of codecs with an improved speech encoding algorithm, which provides enhanced speech quality on full-rate channels


Evolium BSS Description Telecom features

Multiband operation : The same BSS supports:

cells in two different bands (900 and 1800 MHz) each cell having its own BCCH

concentric multi-band cells (900MHz and 1800 MHz TRXs in the same cell) with the outer zone (and the BCCH) in the 900MHz band.


BSC

BSC

BSC

CBE

CBE

Enhanced CBS

CBC

LEGEND

Cell

Broadcast Areas

HMIOMC

S1 : Evolium BSS introduction Telecom features

SMS CB environment

(Short Message Service

Cell Broadcast)


Evolium BSS Description Telecom features

There are two types of Short Message Service (SMS): Point-to-point SMS allows a short message to be sent to, or received from, an

MS. SMS-CB allows messages to be broadcast to the MSs (i.e., one way).

SMS-CB can be used for a number of reasons, e.g. to transmit emergency information, road traffic information, etc. An SMS-CB message can be transmitted to all the cells connected to the BSC, or to selected cells only, as required.


MSC

OMC-R

NMC

S1 : Evolium BSS introduction Operation & Maintenance features

BSS features (1) Multiple Human Machine Interface (HMI) Night time Concentration Secured X25 connection Usage State on Demand BSC Alerter Q3 MultiManager


Evolium BSS Description Operation & Maintenance features

Multiple Human-Machine Interface: This feature permits one OMC-R operator to perform actions normally done by several OMC-Rs, typically during off-duty hours. (X25 network) (Remote Display)

Night Time Concentration: allow an operator to perform alarm management operations for a complete network, where the network consists of more than one OMC-R.

Secured X.25 Connection From BSC to OMC-R: The Secured X.25 Connection feature provides redundant links in the event of a link failure on either the OMC-R or BSC side. When a link failure occurs, the initiator system involved must process the change over. Two physical links, one for Common Management Information Service Elements (CMISE), and one for File Transfer Access and Management (FTAM).

Usage State on Demand: The Usage State on Demand feature allows an OMC-R operator to have a snapshot of the current resource usage at a BSC.

BSC Alerter: The BSC Alerter is a telecom supervision function which generates an alarm event when the system suspects abnormal behaviour of a resource.(ex: TCH - Average occupancy time too long)


BSS features (2)

Online/Offline Hardware Extension/Reduction Provisioning Radio Configuration Performance Management

Indicator/counter Display via MPM (Measurement Performance Management)

OMC-R - MFS support

MSC

OMC-R

Alcatel 9135MFS

S1 : Evolium BSS introduction Operation & Maintenance features


Evolium BSS Description Operation & Maintenance features

Online / Offline Hardware Extension / Reduction (general O&M): let an operator perform hardware configuration operations without having to generate and download a new software package. Online extension / reduction is only available with G2 BSCs.

Provisioning Radio Configuration: let an operator prepare changes on the radio configuration in advance, check them, then activate all the changes as a whole, when he chooses.

Performance Management: Measurement Performances Management (MPM) is based on the NPA functions and characteristic.

Network element provisioning: Being able to differentiate equipment that are not yet in commercial use from equipment under maintenance is of high importance for the network monitoring.


S1 : Evolium BSS introduction Cell Types

Alcatel BSS provides coverage suited to the needs of: Coastal areas

Rural areas

Urban areas

Dense urban areas

Coastal

Extended-Cell

Macro-Cell

Rural & Suburban

Micro-Cell

Urban

In-Building

Indoor-Cell


Cell 1

Cell 3

Cell 2 Sector 2

Sector 3

Sector 1

BTS

Antenna

Umbrella Cell

Urban area

Pedestrianarea

Mini Cellsor micro

900 1800

Cell 1


Sectored site configuration and cells types

Cell split over 2 BTSs:


Evolium BSS Description Cell Types

A sectored BTS site uses a single physical BTS equipped with up to six antennae illuminating six sectors, each covering a separate single macrocell. Figure shows a three-sector arrangement.

The BTS in a sectored site contains up to three transceivers which are each allocated to different given sectors. Each sector and its associated cell are managed independently and are seen functionally, by the OMC and BSC, as separate BTSs connected in chain mode.

Mini cells are used for dense urban areas where traffic hot-spots are covered by very small macrocells (500 m to 1 km radius) and continuous coverage is provided by an overlaid macrocell (5 to 10 km radius). The lower layer mini cells handle pedestrian traffic while the umbrella cell handles the faster moving mobiles. As only macrocells are used there is no street corner effect.



Microcells have a small coverage area (less than 300 m radius). These cells are usually situated indoors or along streets in built-up areas. Microcells have an umbrella cell (1 to 2 km radius) to minimize the risk of losing calls by providing maximum coverage.

Cell split over 2 BTSs: The system is able to handle cells whose TRXs are located in two different BTSs. This feature brings important flexibility by allowing particularly:

To extend an existing site only by adding TRXs in a new BTS, not touching the arrangement of the existing BTS,

To combine existing cells into one, e.g. one 900 cell and one 1800 cell in order to get a multi-band cell,

To support 3x8 TRXs configurations in 2 racks (instead of 3).


SectoredSite Umbrella Cell

Single CellConcentric

Cell

Microcellor

Mini cell Microcellor

Mini cellMicrocell

orMini cell

Umbrella &Concentric

CellMicrocellor

Mini cell Microcellor

Mini cellMicrocell

orMini cell

Extended Cell

Inner Zone

Outer Zone

Inner Cell

Outer CellInner Limit

OverlapZone

Inner CellOuter Limit

Outer Cell

50 km

35 km


Cell Configuration



In the rural and coastal environment coverage is principally a function of cell planning. Standard cell layouts, providing coverage of up to 35 km, include:

Single cells Concentric cells.

Extended cells, which have two co-located antennas, provide options covering traffic density and ranges up to 70 km.

In the urban environment the coverage is determined by the location of the BTS antennae. Two types of cells are normally used:

Macrocells - where the antenna is located above the roof tops and propagation occurs in all directions. These cells can be sectored by using specific antenna patterns.

Microcells - where the antenna is located below roof top level, on building facades or street lights. Propagation occurs mainly as line of sight along the street, with strong attenuation at street corners.

These two cell types can be used in a hierarchical cell environment where continuous coverage is provided by the macrocell (umbrella cell) and locations of increased traffic density are covered by dedicated microcells.


Inner Cell

Highway

Outer Cell70 kmmax

Urban Area

35 kmmax


Example of extended cell topology


GSM-900

GSM-1800

macro macro

umbrella macro

µcells

City center


Example of multiband hierarchical network


Macro GSM 1800

Macro GSM 900

Micro GSM 1800

Fast dualBand MS

Slow dualBand MS

Fast dualBand MS


Example of Handover



Handover occurs more frequently in a microcell environment due to the small radius sizes. Microcell handovers occur:

To handle stationary MSs (especially MSs used indoors). When an MS moves in a street covered by microcells. To avoid losing calls. Whenever there is a risk of losing a call, a

handover is triggered to the umbrella cell.

Fast moving mobiles are handled by the umbrella cell. A mobile handled by a microcell is sent to the umbrella cell if the delay between handovers becomes too small. Conversely a mobile is sent to a microcell if it receives a high level of signal for a sufficient time.

Microcell to microcell handover occurs due to the proximity of the two cells. When the power budget is better in another cell, the MS is handed over to the cell which will serve the call more efficiently. This normally occurs in microcells serving in the same street.


S1 : Evolium BSS introduction Exercises

Give 3 different causes for Handover?

What does the MFS abbreviation mean?

Does the GPRS use packet or circuit switching?

What is the interface between BSC and MFS?

What different types of cell exist in a network?

For Alcatel GPRS solution, what types of equipment do you need?


Session 2

Operation and Maintenance principles


S2 : O&M principles Objective and program

Objective : To identify the local and the network Operation and Maintenance functions.

Program : Operation and maintenance generality BSS O&M terminal functions OMC-R architecture


Evolium™ BSSMSC

OMC-R

MSC

OMC-R


BackboneBackbone

PSTNPSTNBSC

TC

BTS

BTS

MSC

HLR

GGSNGGSNSGSNSGSN

A-bis

Gb

A

S2 : O&M principles Operation and maintenance generality

Operation and Maintenance Center-Radio:

A-ter mux

Alcatel 9135MFS

A-GPSserver

GMLC


BSS maintenance overview:


BTSAbisAbis Atermux A

Gb

IMT

SGSN

BSC TC

MFS(PCU)

MSC

Gb

BTS TerminalBSC Terminal TC Terminal

MSC

OMC-R*


Evolium BSS DescriptionOperation and maintenance generality

There are several types of terminals: BTS terminal BSC terminal OMC-R terminal IMT: Installation and Maintenance Terminal (for MFS)

O&M Architecture The BSS subsystems perform O&M functions, as follows:

The BTS monitors the condition of the hardware modules it manages, and reports any change in status to the BSC.

The BSC supervises its own hardware modules and reports changes in status to the OMC-R.

The BSC and TC provide together a set of transmission O&M functions to ensure a high level of fault tolerance and reliability. The function also provides efficient use of the terrestrial links between the equipment of the BSS.

The MFS, like the BSC, supervises its own hardware modules and reports changes in status to the OMC-R.


SGSN

GGSN

OMC-G

OMC-S MSC/VLRHLR

NMCQ3

MFS

BSS

OMC-R

BSS


A Consistent Approach


MSC

OMC-R

The Way we do GPRS O&M:Alcatel 1353 RA


The OMC-R supervises several BSSs: Manages the BSSs software versions Stores the BSSs configurations Manages fault and performance measurement reports Handles supervision of alarms and events

O&M functions: Configuration Management Performance Management Alarm Management


Evolium BSS DescriptionOperation and maintenance generality

Configuration Management is the process of viewing and controlling network resources. CM allows you to:

Configure the BSS hardware and software when it is first installed Change the network by adding, deleting, or moving network entities. Upgrade to new hardware or software. Change equipment and telecom parameters to improve system performance.

Fault Management Fault Management allows the operator to supervise and to repair the network

when anomalies occur. It does this through a sequence of steps from detection to reporting and recovery. These are carried out by all the BSS subsystems, and are reported to the operator at the OMC-R or at another designated maintenance site.

Performance Management Performance Management allows the operator to monitor the efficiency of the

system and the telecom services. It is controlled entirely from the OMC-R and provides measurements and statistics about various traffic events and resource usage in the BSS.


Alarm Alarm

SurveillanceSurveillanceviewview

Alarms of all MOs of all

BSSs

All cells of all BSSs

Radio Main ViewRadio Main ViewRadio Main ViewRadio Main View

HW equipment view

equipmentrackshelfboard

Functional view

TRECUFU

RSL

BSS-2 Equipment Main ViewBSS-2 Equipment Main View

BSS-1 Equipment Main ViewBSS-1 Equipment Main View

NAVIGATIONNAVIGATION

NAVIGATIONNAVIGATIONNAVIGATIONNAVIGATION

Human Machine Interface

NAVIGATIONNAVIGATION

S2 : O&M principles BSS O&M terminal functions

Fault Management: Network Supervision


S2 : O&M principles OMC-R architecture

External Interfaces

Alcatel 9156 RNO

Alcatel 9155 RNP

Alcatel 1353 RAOMC-R

Alcatel NPA


BSS equivalent rule :

1 BSC eq = 1 BSC G2= 1.5 BSC G1= 1/2 MFS

S2 : O&M principles OMC-R architecture

Alcatel 1353 RA Dimensioning rules

10000

250

750

10

500

1500

20

1200

3600

40

3500

14000

100

1

10

100

1000

SML HOST STD HOST LRG HOST XLRG HOST

CELLTRXBSCEQ

Evolium™ Base Station Subsystem (BSS) Description

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